Flutter学习：使用CustomPaint绘制路径

import 'package:flutter/material.dart';
 
void main() => runApp(MyApp());
 
class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      home: Scaffold(
        appBar: AppBar(
          title: Text('CustomPaint 示例'),
        ),
        body: Center(
          child: CustomPaint(
            size: Size(200, 200),
            painter: MyPainter(),
          ),
        ),
      ),
    );
  }
}
 
class MyPainter extends CustomPainter {
  @override
  void paint(Canvas canvas, Size size) {
    final paint = Paint()
      ..color = Colors.blue
      ..style = PaintingStyle.stroke
      ..strokeWidth = 3.0;
 
    final path = Path();
    path.moveTo(size.width / 2, 0.0); // 移动到画布中心的起始点
    path.lineTo(0.0, size.height); // 绘制一条水平线到画布底部的左侧
    path.lineTo(size.width, size.height); // 绘制一条水平线到画布底部的右侧
    path.close(); // 关闭路径形成一个三角形
 
    canvas.drawPath(path, paint);
  }
 
  @override
  bool shouldRepaint(CustomPainter oldDelegate) {
    return false; // 自定义的绘制不需要重绘时返回false
  }
}

这段代码创建了一个简单的Flutter应用，使用CustomPaint控件和MyPainter自定义绘制类来绘制一个等腰直角三角形。MyPainter类覆盖了paint方法来定义如何绘制路径，并通过shouldRepaint方法指出是否需要重新绘制。这个例子展示了如何使用Flutter的绘图API进行自定义绘制。